The present invention relates to a large scale integrated device used in a computer such as a microcomputer.
A plurality of large scale integrated circuits (to be referred to as LSI for brevity hereafter) which have different independent functions are combined to constitute a system such as a microcomputer. In particular, LSI chips are prepared for a central processing unit for mainly performing arithmetic operations, a read-only memory and a random access memory which have memory functions, and peripheral devices such as a key input control section, a serial I/O section, a parallel I/O section, a counter timing control section, and a display drive section. These LSI chips are mounted on a printed wiring (circuit) board having a predetermined wiring pattern according to the circuit design, thereby electrically connecting the LSI chips to each other. In this manner, a semiconductor circuit system including a plurality of chips having different functions is prepared.
However, according to this conventional system, the wiring pattern often becomes complicated when it is formed on a board in accordance with a predetermined circuit design, resulting in time-consuming manufacturing and high cost. In addition, the electrostatic capacitance of the printed wiring board itself is high, so that signal transmission speed in the wiring pattern becomes low. Even if a high-speed chip having complementary MOS devices is used, high-speed operation of the semiconductor circuit system as a whole cannot be achieved, resulting in inconvenience. Furthermore, the conventional circuit system does not consist of a single chip, so breakdowns frequency occurs.
The above-mentioned drawbacks of the conventional semiconductor circuit system having a plurality of LSI chips on the printed wiring board can be overcome by providing a circuit system without using the printed wiring board. In this case, if known techniques are used, first, the system configuration must be redesigned to prepare a one-chip LSI having all the functions of the conventional LSIs, and second, the conventional chips must be sealed in a single package to constitute a hybrid integrated circuit. However, when redesigning is performed, the design and evaluation processes must be repeated to prepare a one-chip LSI although the conventional LSI chips have proven functions and electrical characteristics. Therefore, the redesigning scheme becomes useless. In addition, redesigning presents other problems such as design errors, a long-term design period and so on. Furthermore, hybrid integrated circuit manufacturing does not provide a good solution to the problem since a ceramic substrate is used in place of the printed wiring board. In practice, it is doubtful whether it is possible to mount the necessary number of chips in a package. Even if such a package is obtained, the manufacturing cost becomes considerably high.